A local area network (LAN) for packet transfer is known from DE 195 32 421 C1. The packet transfer system operates in the asynchronous transfer mode. The local area network includes a plurality of ring systems with one or two rings. A ring system includes a plurality of network nodes which are coupled either via station terminals to a station, or via a network node of another ring system and which are used for switching cells generated by a station or by a network interface. Cells containing address information about the destination, for example, of a certain station are transmitted over a ring. The control procedures in a network node are carried out by at least one controller which is to contain sufficient software structured according to hardware requirements.
When an asynchronous transfer mode is used in a system, payload information, for example television, picture or sound signals are transmitted in fixed-length blocks by arrangements for digital signal processing. A fixed-length block is understood to mean a cell which contains a predefined number of bytes (53 bytes). Each cell includes a header field having a length of 5 bytes, and an information field in which the payload information is accommodated having a length of 48 bytes. In such a header field are contained address information, data for error detection and data for control indication bytes. Address information includes virtual path identifiers and virtual channel identifiers. For transmitting a cell, a virtual channel is rendered available based on the virtual channel identifier (VCI). As a rule, a VCI is changed once a switching center has been reached. A trunk of a plurality of virtual channels is designated a virtual path identifier VPI which is featured by the trunk identifier.
Those skilled in the art are directed to: M. Elixmann et al: "Open Switching--Extending Control Architectures to Facilitate Applications, Proc. of ISS'95, vol. Apr. 2, 1995, pp. 239-243.
The above citations are hereby incorporated in whole by reference.